FILE - This Aug. 25, 2017 file photo shows Detroit Lions quarterback Matthew Stafford looking downfield during the first half of the team's NFL preseason football game against the New England Patriots in Detroit. Stafford has agreed to a five-year extension with the Lions. The team announced Monday, Aug. 28, 2017 the deal keeps the quarterback under contract through the 2022 season. (AP Photo/Rick Osentoski, file)

Robert Mueller’s special counsel investigation into Russian meddling in the 2016 election has cost $6.7 million during the first four and a half months of the probe. Click to see past independent counsel investigations guilty of racking up high bills.